1. Field of the Invention
The present invention relates to a liquid processing method and liquid processing apparatus for performing a liquid process, such as cleaning, on a target substrate, such as a semiconductor wafer or a glass substrate for a flat panel display (FPD), representative of which is a liquid crystal display (LCD). The present invention also relates to a control program and computer readable storage medium for executing a liquid processing method of this kind.
2. Description of the Related Art
In the process of manufacturing semiconductor devices, a cleaning process is performed by supplying a predetermined chemical liquid (cleaning liquid) to clean a semiconductor wafer (which will be simply referred to as “wafer”, hereinafter), so that contaminants, such as particles, organic contaminants, and metal impurities, and polymers remaining after an etching process are removed from the wafer.
As a wafer cleaning apparatus for performing such a cleaning process, a wafer cleaning apparatus of the single-wafer type is known, as follows. Specifically, at first, a chemical liquid is supplied onto the front and back surfaces of a wafer held on a spin chuck, while the wafer is set in a stationary state or in a rotated state, to perform a chemical liquid process. Then, a rinsing liquid, such as purified water, is supplied onto the wafer, while the wafer is rotated at a predetermined rotation number, to wash away the chemical liquid. Then, the wafer is rotated to perform a drying process.
Jpn. Pat. Appln. KOKAI Publication No. 2003-224100 discloses a technique in light of economical efficiency for a wafer cleaning apparatus of the single-wafer type, in which a cleaning process is performed while a chemical liquid puddle (liquid film) is formed on the cleaning target surface of a wafer, so that the chemical liquid consumption can be as little as possible. Specifically, for example, a plate for forming a chemical liquid puddle is disposed to face the back surface of a wafer. Then, while this plate is set to be adjacent to the back surface of the wafer, a chemical liquid is supplied into the gap between the wafer and plate from a nozzle disposed on the plate to form a puddle. The plate is arranged to be movable up and down, so that the plate is moved down, after the chemical liquid cleaning, to expand the gap between the plate and wafer. In this state, a rinsing process and a drying process are performed, while the wafer is rotated at a high speed. During the chemical liquid process, the gap between the plate and wafer is set to be as small as possible to decrease the chemical liquid consumption per wafer.
However, when the plate is moved down to separate it from the wafer, or when the wafer is rotated at a high speed thereafter, the liquid volume within the gap becomes smaller than the gap volume. Consequently, the gap falls into a vacuum state, and the wafer is thereby stuck on the plate and may suffer warp and/or crack generation.